Atherosclerosis and other vascular occlusive diseases are becoming prevalent today in many developed countries. In such diseases, the flow areas of blood vessels become narrowed or occluded by the buildup of plaque on the walls of the vessels, leading to ischemia, and depending upon the location of the vessel, damage to the organ or limb. A number of surgical and percutaneous procedures have been developed for treating stenosis in the coronary arteries and carotid arteries, including endarterectomy, angioplasty, atherectomy and stenting.
One problem frequently encountered during such procedures is that pieces of plaque ("emboli") often are dislodged from the stenosis or the vessel wall. Such emboli may travel inner smaller diameter regions of the vasculature, blocking blood vessels and causing ischemic injury. This problem is especially severe where the emboli are permitted to travel into the coronary arteries and carotid arteries, and can result in infarction, stroke and even death.
Emboli filtration devices are known in which filter elements are deployed against the walls of a vessel distal to a stenosis. Such filters typically comprise a polymer or wire sac mounted on a distal region of a guide wire or angioplasty catheter, and permit blood to flow through the filter while trapping emboli. Once treatment of the stenosis is completed, the filter containing the captured emboli is contracted and withdrawn from the vessel.
For example, U.S. Pat. No. 5,814,064 to Daniel et al. describes an emboli capturing system having a radially expandable mesh filter disposed on the distal end of a guide wire. The filter is deployed distal to a region of stenosis, and any interventional devices, such as an angioplasty balloon or stent delivery system are advanced along the guide wire. The filter is designed to capture emboli generated during treatment of the stenosis while permitting blood to flow through the filter.
U.S. Pat. No. 4,723,549 to Wholey et al. describes an angioplasty catheter having a filter element disposed on its distal end. The filter is supported on a plurality of circumferential struts, and is expanded against the interior wall of a vessel, distal to a stenosis, by an inflation balloon. An angioplasty balloon is disposed on the catheter proximal of the filter for dilating the stenosis. The filter captures emboli dislodged during the dilatation procedure, and then is contracted and removed from the vessel with the angioplasty catheter.
A key disadvantage of previously known emboli filtration systems, such as described in the foregoing patents, is that the filters in those devices are fixedly attached to the guide wire or angioplasty catheter, respectively. If the catheter or guide wire is rotated, bumped or moved after the filter has been deployed, there is a substantial risk that filter will become temporarily dislodged or skewed, thereby permitting emboli to escape past the filter. Moreover, movement of the deployed filter against the vessel wall also may damage the endothelium, and/or dislodge emboli distal to the filter. Such motion is especially likely to occur when other devices such as an angioplasty balloon catheter are deployed along the guide wire after the filter is deployed, as in the Daniels et al. patent.
In view of these disadvantages it would be desirable to provide emboli filtration apparatus and methods having a filter element that remains stationary once deployed.
It also would be desirable to provide emboli filtration apparatus and methods having a filter that may be deployed along a guide wire, but is configured so that subsequent displacements or rotation of the guide wire will not dislodge the filter.
It further would be desirable to provide emboli filtration apparatus and methods that reduce the risk of emboli escaping from a filter element.
It still further would be desirable to provide emboli filtration apparatus and methods that reduce the risk of trauma to vessel endothelium resulting from movement transferred to the emboli filtration apparatus.